reader.preferReaders(prefer)
	}
	defer reader.Done()

	startBlock := offset / e.blockSize
	endBlock := (offset + length) / e.blockSize

	var bytesWritten int64
	var bufs [][]byte
	for block := startBlock; block <= endBlock; block++ {
		var blockOffset, blockLength int64
		switch {
		case startBlock == endBlock:
			blockOffset = offset % e.blockSize
			blockLength = length